SDN Advent Calendar

• スイッチに届く最初のパケットは Unknown なパケットとしてコントローラに送られるだろう（PACKET IN）
• コントローラでは dest MAC をチェックし、それが学習済みのものであれば src MAC と合わせて FLOW MOD (New Flow）を定義するだろう
• src MAC が未知のものであれば、それを学習する（内部テーブルにストアする）
• 当該パケット(1.)を転送するためにコントローラからは PACKET OUT が出るだろう
  （このとき dest MAC が既知なら output は特定ポートを指定し、未知なら Flooding となる）

        out = datapath.ofproto_parser.OFPPacketOut(
            datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions)
        datapath.send_msg(out)
        					

class OFPPacketOut(MsgBase):
    def __init__(self, datapath, buffer_id=None, in_port=None, actions=None,
                 data=None): 
        super(OFPPacketOut, self).__init__(datapath)
        self.buffer_id = buffer_id
        self.in_port = in_port
        self._actions_len = None
        self.actions = actions
        self.data = data    
						

        if msg.buffer_id != ofproto.OFP_NO_BUFFER:
            out = datapath.ofproto_parser.OFPPacketOut(
                datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
                actions=actions)
        else:
            out = datapath.ofproto_parser.OFPPacketOut(
                datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
                actions=actions, data=msg.data)
        datapath.send_msg(out)
						

/* Flow setup and teardown (controller -> datapath). */
struct ofp_flow_mod {
    struct ofp_header header;
    struct ofp_match match;      /* Fields to match */
    uint64_t cookie;             /* Opaque controller-issued identifier. */
    /* Flow actions. */
    uint16_t command;            /* One of OFPFC_*. */
    uint16_t idle_timeout;       /* Idle time before discarding (seconds). */
    uint16_t hard_timeout;       /* Max time before discarding (seconds). */
    uint16_t priority;           /* Priority level of flow entry. */
    uint32_t buffer_id;          /* Buffered packet to apply to (or -1).
                                    Not meaningful for OFPFC_DELETE*. */
    uint16_t out_port;           /* For OFPFC_DELETE* commands, require
                                    matching entries to include this as an
                                    output port.  A value of OFPP_NONE
                                    indicates no restriction. */
    uint16_t flags;              /* One of OFPFF_*. */
    struct ofp_action_header actions[0]; /* The action length is inferred
                                            from the length field in the
                                            header. */
};
OFP_ASSERT(sizeof(struct ofp_flow_mod) == 72);
						

An action_output has the following fields:
/* Action structure for OFPAT_OUTPUT, which sends packets out ’port’.
 * When the ’port’ is the OFPP_CONTROLLER, ’max_len’ indicates the max
 * number of bytes to send.  A ’max_len’ of zero means no bytes of the
 * packet should be sent.*/
struct ofp_action_output {
    uint16_t type;    /* OFPAT_OUTPUT. */
    uint16_t len;     /* Length is 8. */
    uint16_t port;    /* Output port. */
    uint16_t max_len; /* Max length to send to controller. */
};
OFP_ASSERT(sizeof(struct ofp_action_output) == 8);